There was no need to complicate the game, but calling it a mistake is maybe too much. White keeps a clear and stable advantage with 30.a3 or 30.Nc2.
27... g7g8  28. d2e2 Black no longer has time to regroup with Re8-Qd8, as the a5-pawn can simply be captured. 28... a5a4 Trying to complicate the game. 29. b3b4  29... c5a6 